How can I profile Python code line-by-line?

Question

I've been using cProfile to profile my code, and it's been working great. I also use gprof2dot.py to visualize the results (makes it a little clearer).

However, cProfile (and most other Python profilers I've seen so far) seem to only profile at the function-call level. This causes confusion when certain functions are called from different places - I have no idea if call #1 or call #2 is taking up the majority of the time. This gets even worse when the function in question is six levels deep, called from seven other places.

How do I get a line-by-line profiling?

Instead of this:

function #12, total time: 2.0s

I'd like to see something like this:

function #12 (called from somefile.py:102) 0.5s
function #12 (called from main.py:12) 1.5s

cProfile does show how much of the total time "transfers" to the parent, but again this connection is lost when you have a bunch of layers and interconnected calls.

Ideally, I'd love to have a GUI that would parse through the data, then show me my source file with a total time given to each line. Something like this:

main.py:

a = 1 # 0.0s
result = func(a) # 0.4s
c = 1000 # 0.0s
result = func(c) # 5.0s

Then I'd be able to click on the second "func(c)" call to see what's taking up time in that call, separate from the "func(a)" call. Does that make sense?

Answer 1

I believe that's what Robert Kern's line_profiler is intended for. From the link:

File: pystone.py
Function: Proc2 at line 149
Total time: 0.606656 s

Line #      Hits         Time  Per Hit   % Time  Line Contents
==============================================================
   149                                           @profile
   150                                           def Proc2(IntParIO):
   151     50000        82003      1.6     13.5      IntLoc = IntParIO + 10
   152     50000        63162      1.3     10.4      while 1:
   153     50000        69065      1.4     11.4          if Char1Glob == 'A':
   154     50000        66354      1.3     10.9              IntLoc = IntLoc - 1
   155     50000        67263      1.3     11.1              IntParIO = IntLoc - IntGlob
   156     50000        65494      1.3     10.8              EnumLoc = Ident1
   157     50000        68001      1.4     11.2          if EnumLoc == Ident1:
   158     50000        63739      1.3     10.5              break
   159     50000        61575      1.2     10.1      return IntParIO